Interpretive Summary: An attractive alternative stand-alone, wind-electric water pumping system is needed because it is cost prohibitive to extend the electricity from the present utility transmission lines in many rural locations in the United States. Also, an inexpensive way of pumping water for remote villages is needed since it has been estimated that 30% of the world population does not have a safe drinking water supply. Improving the performance of wind-electric water pumping systems without significantly increasing the cost would be beneficial to all remote water users. Installing trailing edge flaps (TEFs) on the blades of a 10 kW wind turbine improved water pumping performance at high wind speeds, but the TEFs also degraded the water pumping performance at low wind speeds. While examining why the TEFs helped water pumping performance at high wind speeds, but hurt performance at low wind speeds, a simpler, less expensive way of improving water pumping performance at all wind speeds was discovered. Aluminum wedges were installed between the blade root and the blade hub which resulted in changing the angle of incidence of the blades with respect to the wind direction. Performance was improved at all wind speeds, thus allowing more water to be pumped without increasing the cost of the wind turbine. Making inexpensive changes to wind turbines used in wind-electric water pumping to improve their performance should result in more people being able to afford a safe water supply.

Technical Abstract:
After testing three trailing edge flap configurations which did not significantly improve the water pumping performance of a wind turbine, additional research was performed to understand why the trailing edge flap configurations were unsuccessful. A camera was mounted at the root of one of the blades with tufts taped to the outboard half of the blade suction surface. Pictures were taken with a remote control device for wind speeds up to 12 m/s. No separation was seen in any of the photos, so vortex generators were not tried. A theoretical analysis of the wind turbine was then begun, and the theoretical power curve came very close to the actual power curve. The theoretical analysis showed that a decrease of four degrees in the pitch angle would result in not only a substantial decrease in the furling wind speed, but also result in an increase in the wind turbine power coefficient from 0.28 to 0.40. Whether these improvements are obtainable will be verified through field testing.